Centrifugal pumps



April 1968 Dv RACHMAN 3,389,390

CENTRIFUGAL PUMPS Filed Mwmh 1966 Sheets-Sheet l l L :[T I l L J IF :IL

April 30, 1968 D. RACHMAN 3,380,390

CENTRIFUGAL PUMPS Filed March 5, 1966 2 Sheets-Sheet United StatesPatent 3,380,390 CENTRIFUGAL PUMPS David Rachman, 29 Melrose.Ave.,Rutherglen, Scotland Filed Mar. 3, 1966, Ser. No. 531,389 2 Claims. (Cl.103113) ABSTRACT OF THE DISCLOSURE A centrifugal pump includes a singleimpeller contained with a pump casing and incorporating blades disposedbetween shrouds having smooth unbroken outer surfaces. One or morenozzles communicating with the discharge side of the pump are directedinto the pump casing and are so located that the line of discharge ofthe nozzle is offset from the axis of the impeller and intersects theouter surface of the shroud at an acute angle such that a jet of liquidissuing from the nozzle will impact against the shroud.

This invention relates to centrifugal pumps and has for an object toprovide a construction intended to facilitate priming of a centrifugalpump and/or to control the operating characteristics of a centrifugalpump and/or to prevent the formation of a vapour lock in the pump.

According to the invention a centrifugal pump having a casing containingan impeller presenting blades located between shrouds incorporates atleast one passage leading from the discharge side of the pump to atleast one nozzle directed into the pump casing and so located that theline of discharge of the nozzle intersects the surface of one of theshrouds.

The pump may be formed with a liquid storage space to which the impellerdischarges, the passage leading from this liquid storage space to thenozzle.

The pump may incorporate several passages leading from the dischargeside of the pump and terminating several nozzles so located on oppositesides of the pump impeller that the line of discharge of each nozzleintersects the shroud on the side of the impeller facing that nozzle.

A practical embodiment of the invention is illustrated in theaccompanying drawings in which FIG. 1 is a vertical longitudinal sectionthrough a pump, and FIG. 2 is an outside elevation.

In the drawings, 1 denotes a pump casing containing an impeller 2 havingblades 3 located between shrouds 4. 5 denotes a chamber located betweenthe discharge end 6 of the pump 6A and a discharge pipe 7 andconstituting a liquid storage space. 3 denotes nozzles formed in thepump casing 1 and disposed to discharge towards the adjacent shroud 4,the nozzles 8 being in communication by a passage 9 with the chamber 5.10 denotes a nonreturn valve of the flap type located in the inletpassage 11 to the impeller.

In practice, the invention may be used mainly for priming a centrifugalpump, liquid from the chamber 5 which is on the discharge side flowingthrough the passage 9 when the pump is set in operation and issuing asjets from the nozzles 8, the jets impinging on the adjacent impellershroud 4 as the impeller 2 rotates. The jets are broken up as theystrike the moving shroud 4 and energy is added to the liquid which isspun off the upper edge of the shroud 4 as a sheet which entrains anyair present,

ice

the entrained air passing along with the liquid into the pump volute 6A.Air in the inlet passage 11 to the pump flows by the shortest route tothe zone of low pressure and thus tends to bypass the impeller 2 andflows towards the nozzles 8 and into the pump volute 6A between theimpeller and the casing. It is known to arrange for the priming of acentrifugal pump by the provision of a return passage leading from aliquid storage space on the discharge side of the pump back to the pumpbut in the known construction the return passage terminates either at apoint adjacent to the impeller inlet or at a point in the vicinity ofthe outer tips of the impeller blades. Disadvantages of the previousconstruction are that where the return passage terminates at the inletof the impeller air entrained from the suction pipe passes through theimpeller passages and causes eddies therein and also once the pump hasbeen primed the return passage must be closed otherwise the operatingefficiency of the pump is severely impaired, and where the returnpassage terminates in the vicinity of the outer tips of the impellerblades the direction of flow through the return passage reverses oncethe pump has become primed. In the construction according to theinvention no reversal of flow takes place under optimum operatingconditions and there is in fact an appreciable increase in pumpperformance after the pump has become primed. The nozzle or each nozzlemay be so proportioned and located that the selfpriming feature is asecondary feature and the main feature provided by the construction isthe increase in pumping performance.

What is claimed is:

1. A centrifugal pump, including at least one pumping stage, having acasing provided with a liquid storage chamber associated with thecasing, an impeller contained within the casing, said impeller havingblades supported between axially spaced shrouds, said shrouds havingsmooth unbroken outer peripheral surfaces, said casing having a nozzledirected at an acute angle to the axis of the impeller toward one ofsaid smooth, unbroken surfaces and a passage means communicating withthe liquid storage chamber whereby liquid will be supplied to saidnozzle and will be directed against said smooth, outer surface to bedischarged at the periphery of said impeller to prevent loss of prime bythe impeller on r04 tation thereof.

2. A centrifugal pump in accordance with claim 1, wherein said casingincludes a plurality of nozzles, each of said nozzles being directed atan acute angle to the axis of the impeller toward one of said smoot h,unbroken surfaces and a like plurality of passage means communicatingwith said liquid storage chamber whereby liquid is supplied to saidnozzles.

References Cited UNITED STATES PATENTS 1,946,212 2/1934 Jacobsen 103 1132,791,968 5/1957 Rupp 103 113 FOREIGN PATENTS 152,673 1922 GreatBritain. 345,973 1931 Great Britain. 368,879 3/1939 Italy. 134,16510/1929 Switzerland.

HENRY F. RADUAZO, Primary Examiner.

